1. Field of the Invention
This invention relates to improvements in well bore drilling operations and more particularly, but not way of limitation to a method and means for simultaneously inserting well casing into and drilling a well bore.
2. Description of the Prior Art
In the present day drilling of an oil and/or gas well bore it is the usual practice to suspend a string of drill pipe from a supporting structure, commonly called a derrick, and connect a drill bit to the lower end of the pipe. The drill pipe is rotated about its own axis by surface equipment commonly known as a kelly, and the rotation of the drill string is transmitted to the drill bit. As the drill bit cuts through or penetrates the earth, the well bore is formed and the weight of the drill string on the bit facilitates the penetration of the bit into the earth for deepening of the well bore. As the depth of the well exceeds the overall lenght of the drill string, it is necessary to add sections of drill pipe to the drill pipe string in order to assure that the drill bit will remain disposed against the bottom of the well bore during the drilling operation. Of course, in the event the drill bit becomes worn or otherwise damaged, it is necessary to elevate the entire drill string within the well bore in order to raise the drill bit to the surface of the ground for repair or replacement. This operation requires considerable time and expensive equipment since the drill string is usually several thousand feet long and quite heavy.
Subsequent to the penetration of the earth by the drill bit through a sufficient depth to drill the well bore to the desired well completion depth, it is necessary to remove the drill string and drill bit from the well bore and lower a string of well casing into the well bore for lining thereof and for receiving the production tubing therethrough. The pulling of the drill string as well as the lowering of the well casing is another time consuming and difficult task, requiring expensive labor and equipment to accomplish.
Another problem encountered in the usual present day well bore drilling method and means is establishment of communication between the surface of the ground and the bottom of the well bore in order to determine certain conditions existing at the bottom of the bore which may be relevant to the overall drilling operation. The most advanced method in use today for determining the conditions within the bore, particularly at the bottom of the bore is a slow, non-continuous, one-way communication system comprising a mud pulse telemetry. This involves the application of a pulse in the drilling mud, or the like, at the bottom of the well bore in order that the pulse may be transmitted upwardly through or by the mud. It will be apparent that some of the pulse is absorbed by the mud, resulting in relatively inaccurate and inefficient returns at the surface of the well.